All over the world the ash and slag of heat power stations are stored in heaps, that turns significant areas of the land to wasteland. As a result of dust formation and burning of heaps of the wastes, the adjoining terrain and air are polluted. Using a hydraulic method for removing the ash and slag (this method remains dominant at modern heat power station) requires significant water consumption. Water after contact with ash has a pH above 10, and contains fluorine, arsenic and vanadium in concentrations, exceeding tolerance. (Vetoshkin A. G. The Protection of the Lithosphere from Contamination. Penza University, 2005). At the present time varied attempts are undertaken to use the slag and ash of heat power stations, working at coal, schist, fuel oil, etc. Slag and ash are used to make curb stones, barrier reefs and blocks for construction, are added to asphalt and are used for other road coverings, as well as additives in the cement industry (Levandovskiy W, Foerborn H. Processing Zoloshlakov TPP. Processing Plant Fly Ash in Europe. The European Association of Combustion of Coal. /ccp.e-apbe.ru/uploads/files/ecoba.pdf). But slags and ash are toxic, their toxicity based on toxicity of incorporated heavy metals. The concentration of oxides of heavy metals in slag and ash is 2-3 times (and sometimes more) higher than the concentration in burnt solid waste or coil, moreover, significant amount of heavy metals are in fly ash: arsenic, barium, beryllium, cadmium, chromium, cobalt, copper, lead, quicksilver, strontium, vanadium, zinc and etc. The toxic heavy metals are released in stable form—the salts or oxides and can remain in the ash for an indeterminate number of years. When heavy metals enter the human body, they lead to different heavy metal diseases. (Yufit S. S. Incinerate Factories—Rubbish Heap in the Sky. Ekoline, 1998).
Very often the determinative parameter in the delivery of ash and slag materials to the consumer is mechanical fuel underburning. As a rule, the majority of heat power stations produce the ash and slag materials with mechanical fuel underburning of 20-30%. Such materials cannot be used. According to, for example, European standards “Fly ash for concrete”, loss on ignition must not exceed 5% of mass. Thereby, in most cases, ash and slag before use must be sorted from surplus or unburned fuel until its content does not exceed 5% of mass. (Tselykovskiy U. K., Environmental and Economic Aspects of Recycling Zoloshlakov TTP. masters.donntu.edu.ua/2009/feht/tihonova/library/article5.htm). If one takes into account that the main mass of unburnt fuel stays within small part clayey material, fritted outside i.e. in vitrified particles, such sorting is a complex process, requiring significant consumption of electric power and capital expenditures. (Calcium Silicate Bricks, Ceramic and Fused Materials Based of Ashes and Slags TTP. /bibliotekar.ru/spravochnik-110stroitelnye-materialy/16.htm).
All modern existing and proposed technologies, more than one hundred of them, do not provide preliminary clearing of the slag and ash from hazardous materials, but only “incapsulating” them (including heavy metals) in body of formed product, not letting, in the opinion of authors, toxic substances to go into the environment. (Knatko V. M., Knatko M. V., Scherbakova E. V. IMM—Technology against Waste./Imitation of Natural Processes of Mineral Formation—a Perspective Direction of Neutralization and Recycling of Industrial Wastes. Energy: Economy, Technique, Ekology. —No 12, 2001, p. 29-35). However, a number of substances forming waste products, for example, sulphur-containing substances can cause degradation of the cement stone that result in diffusion of contaminants into the environment. Besides, toxic metals under certain conditions can be washed away from the storage blocks by rains, for example, when there is a change of acidity of rain water according to “weather conditions” ((Yufit S. S. Incinerate Factories—Rubbish Heap in the Sky. Ekoline, 1998). Since specified toxic substances pertain to more stable toxicants, it is probable that all products, made using the proposed technologies will be toxic for many years. Thereby, even though the results of the studies are positive, they do not give the reasons for broad industrial use of specified technology. Perennial quality checks of concrete products are required even in modern buildings and constructions. Thereby, the problem of rational, ecologically clean use of the slag and ash of heat power station for this moment does not have a satisfactory solution.
According to the United Nations Environment Program annually up to 50 million tons of electronic scrap is not processed, but end up in landfills. (UN Experts Have Adopted a Set of Technical Guidelines on Recycling Mobile Phones Cybersecurity.ru/hard/50582.html. The European Environmental Protection Department has counted that amount of the electronic refuse increases three times more quickly than the average municipal wastes. Computers, mobile telephones and the other device constantly are becoming cheaper and available to more people. The growing consumption of such goods and their rapid obsolescence leads to a constant increase of unwanted electronics (E-waste Threatens the World. Unprofessional Recycling Electronics Pollute Streda solidwaste.ru/news/view/1634.html/7, Mar. 2007. The UNO representatives are urgently concerned with the solution of this problem; otherwise the situation will only become worse. During an investigation, led by an international coalition of ecological organizations, it was realized that enormous amounts of refuse are exported to China, Pakistan and India. So, for example, in the USA annually only 10% of electronic scrap goes into dumps, but up to 80% is transported to developing countries where it is processed by methods harmful to the health of the people and the environment (Computer Landfills Pollute Asia. Feb. 25, 2002 news.bbc.co.uk/hi/russian/sci/tech/newsid—1840587.stm). For example, in coastal province Guandan of China up to 100 thousand migrants break and process the outdated computers from all over the world. In this work participate the men, women and children, not being aware of the harm, which is caused them and to the environment in dismantling of electronics, including incineration under open sky of the plastic parts and wire, use of acid for gold extraction, remelting and incineration of the toxic printed circuit boards, and the release of lead following breaking containing lead cathode beam tubes. Contamination in this region already so great that it is impossible to drink well water, and water necessary to bring by trucks, and written in the report (Poisonous Rubbish of Electronic Revolution. World; guardian.co.uk/online/news/ 23, Sep. 2004; Guiyang—The City of Miners from e Waste (ot.rusk.ru/section/861.
In electric and electronic equipment are used a lot of components, containing such carcinogens, as lead and arsenic, as well as such valuable metals, as copper, bronze, aluminum, silver, palladium, platinum and gold. Small quantities of magnesium, mercury, iridium, niobium, yttrium, titanium, cobalt, chromium, cadmium, tin, selenium, beryllium, tantalum, vanadium and europium are also present. The composition of the multicomponent electronic waste is not constant and depends upon the electronic device types. The main metals form 40% of the general mass of waste and include copper (50%), iron (20%), tin (10%), nickel, lead and aluminum (5% each) and zinc (3%). One ton of the electronic scrap contains an average of 1.8 kg silver, 930 g gold and 45 g palladium. (Chemyuk A. O. Current Status of Extraction of Metals from Scrap Radio Board and Their Cut Products) nbuv.gov.ua/portal/metalurg/2011—23/pdf. As of Swedish Organization of the Recycling “Abfall Schweden” and of Russian State Repository for Precious Metals, in one ton of electronic scrap on the average is present one kilogram of silver, 50 grams of gold and 150 kg of copper, but in one ton of military electronic scrap—500 grams of gold and 300 kg of copper (The Swedes have learned to dig for Gold and Silver from Old Mobile Phones. www.mobiset.ru/Articles; The Effect of “Dabby Dress” Turns Cinderella into a Princess. Business Petersburg, 36 (1145), 4, Mar. 2002)
dpgazeta.ru/article/39565). Note, that gold extraction from scrap is a complex process because gold is present as a fine surface layer on plastic, metallic, ceramic or mixed ceramic-metal base material. However, electronic scrap still contains comparatively more gold, than ore, from which it is extracted. As of Russian State Repository for Precious Metals, household electronic scrap contains in 10-15 times greater of precious metals, for example gold and copper, than ore, but military electronic scrap—has 100 times greater gold and has 30 times greater copper. So processing such stock material is vastly more profitable than processing ore. Even processing of scrap with a low content of gold and other precious metals, the collection and use of valuable components of them is more profitable as a consequence of their high cost. The Computers Will Be Recycled. mtspb.com/production_current.php?id=9&id_group=54).
The problem of salvaging the old electronics in the European Economic Community countries, Japan and USA is of high concern. In these countries there is an enormous amount of legislation encouraging, for example, collection and processing of used mobile telephones. Herewith, however, according to the data of different Ecological Associations in the world presently there are processed only 11% of discarded electronics (Clean the World of Computers. Gazeta.ru. 14, Jul. 2004. mtspb.com/production_current.php?id=9&id_group=54).
This explains why the utilization process to recycle is complex and labor intensive. The first stage in the processing is a sorting, for example, mobile telephones by manufacturers and models. After that the devices are manually disassembled—separating the bodies and other plastic parts, electronics boards, displays, metallic fragments and batteries. From electronic boards the microcircuits, connectors and elements, containing precious metals are removed. Extraction of precious metals from these components is performed by different electrochemical methods. Hereafter recovered precious metals are sent to specialized plants for additional purification. Plastic and metallic elements of bodies and the remainder of the printed boards are at the beginning crushed into small pieces, but then ground to dust, and sorted by the mechanical methods. More light dust from plastic elements is separated from “heavy” metallic dust. At this stage processing ends—sorted dust goes to processing enterprises, where it is used in production of different products. After similar conversions into secondary use goes 80-90% of the cellular telephone. The recycling of used batteries and the dumping of remaining wastes remains a concern for many specific enterprises (Golovanova N., Mobile Scrap: for Verge of the Lives. What Utilization Come to Pass. Mforum.ru. 19, Nov. 2008). An advantage of the technology is that metal extraction from electronic scrap is ten times cheaper, than extraction from ore. An important disadvantage, however, is the contamination of the environment with dusty particles of scrap, using the time and labor-consuming manual labor in process of the device disassembling at processing of superficially humid scrap due to adhesion of particles of dust makes it impossible to obtain qualitative separation to different fractions what leads to loss precious metals, and in event of the following processing of plastic dust by thermal methods, for example by pyrolysis, inevitably the formation of dioxins, pollutes the environment. Besides, high probability of the formation explosive mixture of dry dust with air at detritions, sorting and transportation by mechanical methods exists so that an electric spark can cause an explosion and destruction of the equipment.
This is explained as follows. In many branches of industry, during processing and transportation of free-flowing dielectric materials the phenomenon of static-charge accumulation by friction of the particles one on another and on air during motion exist. Electrization of material prevents the normal flow of the technological processes, as well as creates an additional fire danger as a consequence of spark formation at discharge. Grounding of the metallic parts of the equipment, increases surfaces and volume conductivity of the dielectric materials, and prevents the accumulation of significant steady-state charge by installation in a zone of electrical protection, special neutralizers which, however, frequently can not provide full electrostatic spark safety. Therefore it is overwhelmingly important to provide conditions, including electrostatic spark safety as a condition of the method, where there is a possibility of explosion and fire from static electricity is excluded (Static Electricity. The Section Overview. na5.ru/500709-1).
The known pyrometallurgical conversion of electronic industry scrap, include its firing in a rotating converter at a temperature of 1250-1350° C. for the purpose of removing organic material, in particular plastics. The gases, which evolve during firing, burn up in an afterburner chamber and are cleared from dust. After removing organic impurities, after firing scoria into a converter copper scrap and fuse are loaded. Then, the metal is blown out by oxygen for removing the metal admixtures (the iron, lead, zinc and others) and directed to the production of anodes (Scott Yames, Sabin Metal Corporation; Scotts Vilce, NY. Pyrometallurgical Conversion of Electronic Industry Scrap. The Material of 19th International Conference on Precious Metals. Incline Village, Nev., USA, 1995). An important disadvantage of the specified way is the impossibility to catch all released dioxins, greater investments and maintenance costs, related to complexity of used equipment, low productivity and high power consumption of the process.
Processes for the conversion of electronics scrap, electrical devices and equipment, consisting of organic and inorganic components, including toxic heavy metals and polychlorinated biphenyls are well known. The methods provide crushing of the scrap up to size of the particles 5-25 mm, thermal processing at the temperature 350-600° and pressure 100 kP-10 mP (1-100/sm2) with a simultaneous mixing operation up to 10 minutes. As a result of depolymerizing and thermal decomposition the organic vapors and gases and solid residues of pyrolysis with a high concentration of basic and precious metals are obtained (U.S. Pat. No. 7,407,122). An important disadvantage of this technology is the presence of dioxins and heavy metals in gaseous fractions and dioxins in the solid fraction of the final products, and the high power requirements of the process.
The known method and device for extraction material from electronic and electrical scrap, including frequent crushing, division by mechanical and physical methods by cyclones and electrostatic separators with the following reception of the nonmetallic faction in the form of granules and dust and metallic faction, going after on processing by electrolytic and chemical methods or simple melting (U.S. Pat. No. 5,139,203). An advantage of the method is a high degree of division of metallic faction from nonmetallic, that allows to process the metallic faction of scrap by simple melting without using metallurgical reactions. Important disadvantage of technology—an environment contamination by dusty particles of scrap, as well as a high probability of the formation of an explosive mixture of dry dust with air, after sorting and transportation by mechanical methods so that an electric spark can cause an explosion and destruction of the equipment. After processing of superficially humid scrap due to adhesion of dust particles, it is impossible to obtain qualitative fractions separations and that leads to precious metals loss. Besides, in the event of the following processing of plastic dust by thermal methods, for example by pyrolysis, inevitably formation of dioxins results, which pollutes the environment.
The Japanese scientists from Saga University created inexpensive and efficient gels, which are capable of removing from rubbish, microparticles of precious metals. It turned out that the gel “separates out” nearly 90% of gold, platinum and palladium, herewith leaving behind copper, zinc and iron. Important disadvantage revealed by Japanese chemists—a low velocity of occurring processes. The kinetic restrictions make it impossible to widely use the gels in industry The New Gel is Making Gold with Newspapers. membrana.ru/particle/12761.
The specialists at NEC (Nippon Electric Company) have developed a new system of extraction of useful components from discarded printed circuit boards. The process known as “EcoSeparation System” consists of two main stages: EcoRemover, in the course of which mounted on printed boards electronic components mounted on the printed circuit boards, are removed, and EcoSeparation, which includes pulverizing of the boards and separation of the obtained mixture of materials. On the first stage, EcoRemover, the boards are heated up to the melting temperature of solder; fluid solder is drawn off and installed on board components which are separated from it with a small external effort. According to statements of NEC representatives, 95% of solder was collected in the course of test and separation of nearly all components from the boards without any losses. Thereafter, the stripped printed boards are transported to the second stage. As a result of realization of the process EcoSeparation it is reduced in to powder, which is then divided according to two methods: using an air centrifuge and an electrostatic high-voltage filter. The process succeeds in collection of more than 98% copper contained in printed circuit boards; nearly 100% of the fiberglass and of the adhesive resins, which are suitable for recycling end secondary use (NEC launches the “Ecoseparation System”. Newsbytes. 28 Nov. 2002). Important disadvantages of technology is an environmental contamination by dusty particles of scrap, the need to use manual labor in a process of disassembling of devices for separation of the electronic boards, the possibility of the explosive mixture formation of dry dust with air in an air-centrifuge which after an electric spark can explode and destroy the equipment. After processing of superficially humid scrap due to adhesion of dust particles it is impossible to obtain qualitative division to separate fractions what leads to loss of precious metals. Besides, in the event of the following conversion of plastic dust by thermal methods, for example by pyrolysis, inevitably formation of dioxins occurs, polluting the environment.
The known method of the extraction of the precious metals from printed circuits, includes heating of the specified circuits up to the temperature of the melting solder, separation of the integral microcircuits, electro- and radio-elements from printed boards by shaking, magnetic separation with separation of the specified microcircuits, breaking them into pieces by crushing. The obtained product is subject to additional magnetic separation with allocation of the concentrate of the precious metals, which makes it possible to direct hydro-, pyro-metallurgical or plasma-chemical processing for separation of each type of the precious metal (See Russian Patent No. 2068010). An advantage of technology is that in crushing of the plastic bodies, their embrittlement occurs without breaching the whole microcircuits to provide a good extraction of the concentrate of the precious metals, incorporated in specified microcircuits, without using electric or air separation. An important disadvantage is the need to use manual labor in the process for disassembling the devices, as well as formation of dioxins, which pollute the environment, during and following processing of plastic by thermal methods, for example by pyrolysis.
The known method of the processing and recovery of electronic and electrical scrap includes providing preliminary thermal processing and removing installed on board components, crushing and separating on a strainer to particles by size 3-13 mm and more 13 mm. Particles more than 13 mm are returned for repeated crushing, particles less than 3 mm—go to a collector of dust, but particles 3-13 mm—undergo magnetic separation to give magnetic and non magnetic factions. After such a separation, repeated pulverizing, multistage separation using a strainer, separation using magnetic and electrostatic separators to obtain the base material, ceramic material and precious metals (U.S. Pat. No. 5,547,134). Important disadvantages of this method include environmental contamination by dusty particles of scrap, use of manual labor in the process of the electronic boards separation, the possibility of explosive mixture formation of dry dust with air which after an electric spark is subject to explosion and destruction of the equipment. After processing of superficially humid scrap which includes adhesion of particles of dust, it is impossible to obtain a qualitative division into separate fractions and so this leads to precious metals loss. Besides, in the event of the following processing of plastic dust by thermal methods, for example by pyrolysis, the result in inevitable formation of dioxins, which pollutes the environment.
The specialists at “Mechanobr-technology” have developed technology for the electromechanic processing of electronic and cable scrap. Outdated computers, television sets, and refrigerators, for example, in other words, all devices and electronic circuit enter the shredder wholly. The line contains the knife grinder, the knocked-rotary grinder of the first stage and the same grinder of second stage, where material is by force reduced to 5 mm granules. Hereinafter a drum bolting machine is installed, working in a closed cycle with a grinder and magnetic separator, which separates from product of the crushing intergrown pieces of magnetic metal with precious metals. Nonmagnetic material enters the electrostatic separator, where all metals are separated from nonmetal on the basis of electrical conductivity. Dust, forming during the process of the crushing and separation, is extracted by built-in aspiration system. From nonmagnetic metallic concentrates at another plant on base of hydrometallurgical process precious and non-ferrous metals are obtained (The Effect of “Dabby Dress” Turns Cinderella in a Princess. Business Petersburg, 36 (1145), 4, Mar. 2002. dpgazcta.ru.article/39565; The Complex of equipment for processing and sorting of electronic, electrical and cable scrap. mtspb.com/production_current.php?id=98id_group=54; The Computers Will Recycle. strf.ru/science.uspx?cataloged=222&d. Dignity of the technology—an exception of low productive manual breakdown of the devices. Important disadvantages of technology include that even in the presence of built-in aspiration system for extraction of dust high probability of explosive mixture formation of dry dust with air that at electric spark can cause explosion and destroy the equipment, contamination of the environment by dusty particle of scrap. Besides, in the event of the following conversion of plastic by thermal methods, for example by pyrolysis, inevitably formation of dioxins, pollute the environment.
The known methods of processing electronic and cable scrap, for example, radioelectronics scrap and electronic game equipment with extraction from them metals and sorting of plastics, includes crushing, pulverizing in hammer grinders in closed cycle with air and sieve separation by size, render particles of the material to a size smaller then 5 mm and separation by electrostatic method to electrically conductive metallic and dielectric fractions and semi-product, which returns to the repeated crushing and separation (Russian Patent No. 2166376). Advantages of the method include high efficiency of the metal separation from basic material and, accordingly, its minimum losses. Important disadvantages of the technology include environmental contamination by dusty particle of scrap, the probability of the explosive mixture formation by dry dust with air so that an electric spark may cause explosion and destruction of the equipment. After processing of superficially humid scrap because of particles of dust adhesion, it is impossible to obtain qualitative separation to separate fractions that leads to loss of precious metals. Besides, in the event of the following processing of plastic dust by thermal methods, for example by pyrolysis, inevitably formation of dioxins occurs, polluting the environment.
The known processes, require pulverizing electronic and cable scrap, separating an obtained powder in an air classifier and cyclones to obtain a significant amount and quality of metal fractions, having different physical characteristics. The cycle of the complex by air—closed with a reset of an extra amount of air through a cyclone and vortex gas scrubber into the atmosphere (Catalogue of Industrial Equipment for Reception Powder and Mixtures. Bolting Machines. Units. Classification of Powders to Produce the Required Quantity and Quality of Product Fractions. (pomol.ru). Important disadvantages include a high probability of an explosive mixture formation of dry dust with air so that following an electric spark an explosion may occur which destroys the equipment. After processing of superficially humid scrap which includes adhesion of dust particles, it is impossible to obtain qualitative separation to separate fractions that leads to loss of precious metals. Besides, even using a closed cycle by air with wet purification in gas scrubber of part of the air, discharge in to atmosphere, it is not enough to protect the environment from contamination by dusty particles of the scrap, but adding water after the scrubbing is necessary to clean or discharge in to sewerage. In the event of the following processing of plastic dust by thermal methods, for example by pyrolysis, inevitably formation of dioxins occur, which pollutes the environment.
The Company “Zhengyuan Powder Equipment” offers for processing and separation of superficially humid material as injectant the air, beforehand dried by the freeze-out (Zhengyuan Powder Engineering Equipment Co., Ltd. The Equipment Catalogue. The Block Diagram No. 1 and No. 2 with the Freeze-Out Drying Machine (chinamill.ru). Drying process of the air excludes adhesion of the dust particles and, accordingly, raises the quality of finely dispersed powder separation on fractions. The important disadvantages include a significant expense for installation and maintenance of the equipment of the dried the air by freeze-out, environment contamination by dusty particle of scrap and high probability of explosive mixture formation by dry dust with by air that fo destruction the equipment. Besides, in the event of the following processing of plastic dust by thermal methods, for example by pyrolysis, inevitably formation of dioxins occurs, polluting the environment.
The same company offers for processing and division of the fire and explosion hazardous materials as injectant instead the air to use the inert gas, for example, nitrogen. The process includes a reservoir and a source of nitrogen, nitrogen-compressor, jet mill, dedusting cyclone, pulsed deduster and the automation system (Zhengyuan Powder Engineering Equipment Co., Ltd. The Equipment Catalogue. Explosion Prevention Flow Chart (chinamill.ru). Such decision really provides overall protection of the work. However, the process vastly increases the cost of electronic and cable scrap processing due to expenses of the nitrogen production, installation of the extra equipment and creation of a completely airproof unit. Besides, in the event of the following processing of plastic by thermal methods, for example by pyrolysis, inevitably formation of dioxins occurs, polluting the environment.
The electric charges, forming on parts of the equipment, as a result of friction of particles material about one another about air and equipment during motion, can be mutually neutralized as a consequence of a certain conductivity of the humid air, as well as flow down to the land on surfaces of the equipment, but in some cases, when charges are great and the difference in potential is also great, that in view of the low moisture content of the air, a rapid electric spark can occur between electrified parts of the equipment or to the land. The energy of such a spark can be sufficient for ignition of a combustible or explosive mixture. Exceedingly it is important that under relative moisture of the air 85% and more sparks of the static electricity are absent (Static Electricity. The Section Overview. (na5.ru/500709-1) Thereby, high relative moisture of the air provides non-explosive working of the equipment for processing and transportation of loose materials. However, due to moisture condensations of humid air and, accordingly, adhesion of the dust particles occurs, and so it is impossible to obtain qualitative separation to separate factions which leads to losses, for example, of precious metal and stoppage of use of the equipment for required cleaning to remove the particles adhering to the machinery.
The known method and plant for waste processing, including electronic, electric and cable scrap, provided their preliminary crushing, separation of the ferrous metals, mix with limestone and drying-up (U.S. Pat. No. 7,611,576). The process of pyrolysis is realized in two stages with simultaneous neutralization of discharging hydrogen chloride by limestone that excludes formation and, accordingly, emission of dioxins to environment, but clear of washing water after solid products of pyrolysis extracting excludes the discharge of the heavy metals (including nonferrous and precious) in environment. The important disadvantage of specified technology:                is not provided separation of nonferrous and precious metals from electronic, electric and cable scrap, entering for processing together with municipal waste;        is not designed efficient circuit diagrams of the technological processes and equipment for raw materials preparation—mixing of solid municipal waste and limestone before feed in dryer and pollution of water from salts of heavy metals;        drying of municipal waste and limestone mixture is realized in two stages—by hot air, which has been heated up due to utilizing of the heat of chimney gases from a furnace of pyrolysis and then mixing with a part of a solid product of pyrolysis (recycle), outgoing from furnace of pyrolysis. Drying of solid product of pyrolysis after its washing and centrifuging is realized by mixing with a part of hot slag (recycle), outgoing from combustion chamber. Herewith it is necessary to remove the metered-in amount of the solid products of pyrolysis and slag (that is only part from the total amount) automatically, moreover, having provided hermeticity of channels (sluicing). After that washed solid remainder of pyrolysis and slag must be transported to the combustion chamber, and heated up again. This is possible, but in a complicated way;        is not shown possibility of the slag and ash processing of the heat power station and industrial boiler plant, working at solid fuels;        a water supply of the steam recovery boilers realized by industrial condensate, containing calcium chloride that leads to quick incrustation on heat surfaces, frequent stoppage of recovery boilers for washing and cleaning and, accordingly, stopping operation of the whole plant.        